Extra-virgin olive oil, as needed
4 skin-on salmon fillets, 5 to 6 ounces each
1/2 teaspoon sea salt
Freshly ground pepper, to taste
1 small spring onion or 2 scallions, roots trimmed and discarded, remaining portions thinly sliced
4 thin lemon slices
24 small cherry tomatoes, halved
8 thin slices fennel bulb
4 thin, peeled, quarter-sized slices fresh ginger
4 large, fresh basil leaves
Preheat oven to 425 F. Cut 4 (12-inch) squares of heavy-duty aluminum foil, place shiny sides down on a work surface and brush some of the olive oil in center of each square.
Brush flesh sides of each of the salmon fillets with olive oil and put a fillet, skin side down, on each foil square. Season fillets with the salt and pepper. Top each fillet with one-fourth of the onion, a lemon slice, a dozen tomato halves, 2 fennel slices, a ginger slice and a basil leaf, scattering ingredients over and around salmon. Bring edges of foil together and fold to seal packages securely.
Place foil packages on a baking sheet and bake in preheated oven for 15 to 18 minutes. Unseal a package (be careful, as steam will be hot) to check for doneness. If necessary, reseal and return to oven for 1 to 2 minutes.
Unseal packages. Transfer contents of each to shallow bowls, pouring any juices over fish.
Makes 4 servings.